1. Field
The present disclosure relates generally to aircraft and, in particular, to aircraft engines. Still more particularly, the present disclosure relates to a method and apparatus for changing the direction of gases exiting a nozzle for an aircraft engine.
2. Background
Noise caused by aircraft near airports is a source of noise pollution. As an engine for a jet operates, the engine generates a flow of gases to move the aircraft. The flow of gases generated by the engine may also be referred to as a plume or exhaust for the engine. With respect to the noise caused by aircraft, the engine exhaust in aircraft makes up a large amount of the noise produced by the aircraft during takeoff.
A number of different mechanisms have been used to reduce the amount of noise. These mechanisms include altering the flow of the gases generated by the engine. The exit area of the fan nozzle may be increased during takeoff to reduce the noise from the exhaust.
One mechanism includes moving the nozzle of the engine in a linear direction towards the aft of the aircraft. This movement of the nozzle is parallel to a longitudinal axis of the engine. This type of movement of the nozzle may increase the exit area of the nozzle and reduce the speed of the exhaust. The reduction in the speed of the exhaust reduces the noise generated by the engine.
However, this type of mechanism may have a number of drawbacks. For example, by moving the nozzle in a direction towards the aft of the aircraft, an opening may be created. This opening may result in a leakage through the engine that reduces the thrust generated by the engine. As a result, the performance of the engine may be reduced. This reduction may reduce the fuel efficiency and increase the cost of operating the engine.
If seals are used to reduce leakage, maintenance of the seals is performed. This maintenance may increase how long an aircraft is out of service and increase the operating costs for the aircraft.
Further, this type of mechanism may involve a movement of the nozzle between a stowed and deployed position to provide a desired amount of noise reduction and a desired amount of thrust during takeoff. This type of movement may have clearance issues between the movement of the nozzle and control surfaces on the trailing edge of a wing of the aircraft.
Another approach currently used may include increasing the exit area by implementing flaps that expand. These flaps may be pivoted outward and reduce the exhaust velocity. These types of flaps may be biased to one side or the other side to provide the desired amount of thrust in the desired direction for maneuvering the aircraft. This type of mechanism, however, may increase the weight, maintenance, complexity, and cost of an aircraft engine.
Therefore, it would be desirable to have a method and apparatus that takes into account one or more of the issues discussed above, as well as possibly other issues.